This invention relates to novel polysaccharide derivatives and to their method of production. More particularly, it concerns the preparation of new polysaccharide derivatives that are hydrophohic and strongly lipophilic, and which consequently are outstanding substrates for liquid-gel chromatography.
In the technique of liquid-gel chromatography, mixtures of lipids, steroids, enzymes, or like biological materials are resolved by selective elution through a column packed with an immobile substrate, or stationary phase, composed of an insoluble polymer having functional groups. Separation of the mixture components is effected by the greater or lesser degree of attraction between the individual component and the functional groups on the substrate.
Because of the variety of biological mixtures likely to be encountered, and because of the different eluting solvent systems employed, it is necessary to provide substrates which are unaffected by water (hydrophobic) yet are solvated by organic solvents and have a relatively strong affinity for the organic biologicals (lipophlic). Additionally, it is desirable to provide a substrate which can be modified for specific separations by substitution with various functional groups.
Attempts have been made to produce hydrophobic and strongly lipophilic substrates from polysaccharides, especially from cellulose and dextran. By known procedures it is possible to produce some types of derivatives, e.g. esters, but for many applications the physical characteristics and the greater chemical stability of the ether derivatives are desirable or necessary. Although polysaccharides combine readily with short-chain epoxides in alkali-catalyzed reactions to produce weakly lipophilic ether-substituted derivatives, these products are not well solvated by the very nonpolar solvents (e.g. heptane) and do not possess hydrophobic properties. Longer chain epoxides have not been found to react readily with the hydroxyl groups of polysaccharides under alkaline conditions. This lack of reactivity is due primarily to the greatly differing solvation characteristics of the polysaccharide and the epoxide, thus considerably limiting the amounts of catalyst and reagents participating in the actual reaction. Additionally, hydrogen bonding within the polysaccharide matrix prevents solvation and interaction with most acidic catalysts and organic reaction media.
Therefore, until now it has been difficult or impossible with known methods to produce hydrophobic, strongly lipophilic, products containing stable ether linkages from polysaccharide materials.